openssl_rsa_aes_encrypt.rb

require 'openssl'
require 'yaml'

class Encryptor
  
  def initialize(key_pass, key_size = 2048, key_name = 'rsakey.sec', cipher = OpenSSL::Cipher.new('aes-256-cbc'))
    @key_size = key_size
    @cipher = cipher
    @key_name = key_name

    if( File.exists?(@key_name) )
      @rsakey = OpenSSL::PKey::RSA.new(File.read(@key_name), key_pass)
    else
      @rsakey = OpenSSL::PKey::RSA.generate(@key_size)
      File.open(@key_name,'w+') do |priv|
        priv.write(@rsakey.to_pem(@cipher, key_pass))
      end
    end
  end

  def rsa_encrypt(txt, pub_key=nil)
    begin
      pub_key.nil? ? @rsakey.public_encrypt(txt) : OpenSSL::PKey::RSA.new(pub_key).public_encrypt(txt)
    rescue OpenSSL::PKey::RSAError => e
      if e.message == 'data too large for key size'
        STDERR.puts 'Your string is too large to encrypt'
      else
        raise
      end
    end
  end

  def rsa_decrypt(etxt)
    @rsakey.private_decrypt(etxt)
  end

  def aes_encrypt(txt, aes_file)
    key = get_aes_key(aes_file)
    cif = OpenSSL::Cipher.new('AES-256-CBC')
    cif.encrypt
    cif.key = key[:key]
    cif.iv  = key[:iv] = cif.random_iv
    save_aes_key(aes_file, key)
    etxt = ''
    etxt << cif.update(txt)
    etxt << cif.final
    etxt
  end

  def aes_decrypt(etxt, aes_file)
    key = get_aes_key(aes_file)
    cif = OpenSSL::Cipher.new('AES-256-CBC')
    cif.decrypt
    cif.key = key[:key]
    cif.iv  = key[:iv]
    txt = ''
    txt << cif.update(etxt)
    txt << cif.final
    txt
  end

  def gen_aes_key(file)
    cif = OpenSSL::Cipher.new('AES-256-CBC')
    key = {key: cif.random_key}
    save_aes_key(file, key)
    key
  end

  def save_aes_key(file,key_iv) 
    File.open(file,'w+') do |f|
      f.write(rsa_encrypt(YAML.dump(key_iv)))
    end
  end

  def get_aes_key(file)
    YAML.load(rsa_decrypt(File.read(file)))
  end
  
  def give_aes_key(aes_file, rsa_pub)
    aes = get_aes_key(aes_file)
    rsa_encrypt(YAML.dump(aes), rsa_pub)
  end

end